I just picked up my sleeping kobo and accidentally pressed one of the buttons on the side. I noticed a flash of the blue led. So out of interest I pushed a few other buttons and the led flashed for them too. When I finally resumed from sleep I was back at the page I left.

I'm not sure what this means. I thought that the purpose of sleep mode was to essentially have the device using little power and only responding to the power button. But it looks like all buttons are active and the processor is actively responding in some way. I wonder if this has power saving implications?